Entity Central Index Key Document and entity information. Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Statement Of Financial Position [Abstract] Statement [Table] Statement [Table] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Convertible Preferred Stock Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Short-term investments Available For Sale Securities Current Accounts receivable Accounts Receivable Net Current Prepaid expenses and other current assets Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Intangible assets, net Indefinite Lived Intangible Assets Excluding Goodwill Goodwill Goodwill Restricted cash Restricted Cash Noncurrent Other assets Other Assets Noncurrent Total assets Assets Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Income tax payable Taxes Payable Current Accrued liabilities Accrued Liabilities Current Deferred revenue, current portion Contract With Customer Liability Current Total current liabilities Liabilities Current Deferred revenue, net of current portion Contract With Customer Liability Noncurrent Other long-term liabilities Other Liabilities Noncurrent Total liabilities Liabilities Commitments and contingencies Commitments And Contingencies Stockholders' equity: Stockholders Equity [Abstract] Convertible preferred stock, $0.00001 par value; 10,000,000 shares authorized and no shares issued and outstanding at September 30, 2018 and December 31, 2017. Preferred Stock Value Common stock, $0.00001 par value; 75,000,000 shares authorized; 44,997,279 and 38,478,560 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Accumulated other comprehensive loss Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders' equity Stockholders Equity Total liabilities and stockholders' equity Liabilities And Stockholders Equity Convertible Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Convertible Preferred stock, shares authorized Preferred Stock Shares Authorized Convertible Preferred stock, shares issued Preferred Stock Shares Issued Convertible Preferred stock, shares outstanding Preferred Stock Shares Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Statement Of Income And Comprehensive Income [Abstract] Product and Service Product Or Service [Axis] Product and Service Products And Services [Domain] License and Service License And Service [Member] Revenue Revenue From Contract With Customer Excluding Assessed Tax Revenue from related party Revenue From Related Parties Total revenue Revenues Operating expenses: Operating Expenses [Abstract] Research and development Research And Development Expense General and administrative General And Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income Loss Interest income Investment Income Interest Other income (expense), net Other Nonoperating Income Expense Loss before provision for income taxes Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Provision for (benefit from) income taxes Income Tax Expense Benefit Net loss Net Income Loss Net loss per share, basic and diluted Income Loss From Continuing Operations Per Basic And Diluted Share Shares used to compute net loss per share, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Other comprehensive income (loss): Other Comprehensive Income Loss Tax [Abstract] Changes in unrealized gains (losses) on short-term investments Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Comprehensive loss Comprehensive Income Net Of Tax Increase (decrease) in accrued liabilities, income tax payable and other liabilities noncurrent. Non-cash acquisition in process research and development asset charged to expense. Noncash or part noncash adjustment to deferred revenue resulting from adoption of accounting pronouncements. Statement Of Cash Flows [Abstract] Adjustments for New Accounting Pronouncements Adjustments For New Accounting Pronouncements [Axis] Type of Adoption Type Of Adoption [Member] ASC 606 Accounting Standards Update201409 [Member] Cash flows from operating activities: Net Cash Provided By Used In Operating Activities [Abstract] Net loss Adjustments to reconcile net loss to net cash (used in) provided by operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Gain on disposal of property and equipment Gain Loss On Sale Of Property Plant Equipment Amortization of intangible assets Amortization Of Intangible Assets Depreciation and amortization Depreciation And Amortization Amortization of premiums (accretion of discounts) on investments Accretion Amortization Of Discounts And Premiums Investments Stock-based compensation expense Share Based Compensation Non-cash acquisition of in-process research and development asset charged to expense Research And Development In Process Deferred income taxes Deferred Income Taxes And Tax Credits Changes in operating assets and liabilities Increase Decrease In Operating Capital [Abstract] Accounts receivable Increase Decrease In Accounts Receivable Related party accounts receivable Increase Decrease In Accounts Receivable Related Parties Prepaid expenses and other current assets Increase Decrease In Prepaid Deferred Expense And Other Assets Other assets Increase Decrease In Other Operating Assets Accounts payable Increase Decrease In Accounts Payable Accrued liabilities, income tax payable and other long-term liabilities Increase Decrease In Accrued Liabilities Income Tax Payable And Other Liabilities Noncurrent Deferred revenue Increase Decrease In Deferred Revenue Net cash (used in) provided by operating activities Net Cash Provided By Used In Operating Activities Cash flows from investing activities: Net Cash Provided By Used In Investing Activities [Abstract] Purchases of property and equipment Payments To Acquire Property Plant And Equipment Purchases of short-term investments Payments To Acquire Available For Sale Securities Maturities of short-term investments Proceeds From Sale And Maturity Of Available For Sale Securities Net cash (used in) provided by investing activities Net Cash Provided By Used In Investing Activities Cash flows from financing activities: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from common stock issuance, net of underwriting discounts and issuance costs of $9,154 Proceeds From Issuance Of Common Stock Proceeds from exercise of stock options and employee stock purchases Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Net increase in cash, cash equivalents and restricted cash Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Cash, cash equivalents and restricted cash, beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash, cash equivalents and restricted cash, end of period Supplemental disclosures of noncash investing and financing items: Noncash Investing And Financing Items [Abstract] Purchases of property and equipment in accounts payable and accrued liabilities Capital Expenditures Incurred But Not Yet Paid Non-cash acquisition of in-process research and development asset charged to expense Noncash Acquisition In Process Research And Development Asset Charged To Expense Non-cash adjustment to deferred revenue resulting from the adoption of ASC 606 Noncash Or Part Noncash Adjustment To Deferred Revenue Resulting From Adoption Of Accounting Pronouncements Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock Common Stock [Member] Underwriting discounts and issuance costs Payments Of Stock Issuance Costs Organization Consolidation And Presentation Of Financial Statements [Abstract] Description of the Business Nature Of Operations Accounting Policies [Abstract] Basis of Presentation and Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements and Short-Term Investments Fair Value Disclosures [Text Block] Accrued Liabilities Current [Abstract] Accrued Liabilities Accounts Payable And Accrued Liabilities Disclosure [Text Block] Research and collaboration agreements. Research and Collaboration Agreements Research And Collaboration Agreements [Text Block] License agreement. Research And Development [Abstract] License Agreement License Agreement Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock-Based Compensation Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Earnings Per Share [Abstract] Net Loss Per Share Earnings Per Share [Text Block] Income Tax Disclosure [Abstract] Income Tax Expense Income Tax Disclosure [Text Block] Basis of Presentation Basis Of Accounting Policy Policy [Text Block] Unaudited interim financial information. Unaudited Interim Financial Information Unaudited Interim Financial Information Policy [Text Block] Use of Estimates Use Of Estimates Cash and Cash Equivalents Cash And Cash Equivalents Policy [Text Block] Restricted Cash Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Contract Balances Revenue Recognition Deferred Revenue Comprehensive Income (Loss) Comprehensive Income Policy Policy [Text Block] Revenue Recognition Revenue Recognition Policy [Text Block] Adopted Accounting Pronouncements and Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Schedule of cash, cash equivalents, and restricted cash. Summary of Reconciliation of Cash, Cash Equivalents, and Restricted Cash Schedule Of Cash Cash Equivalents And Restricted Cash Table [Text Block] Summary Impact of Adopting ASC 606 on Select Unaudited Financial Statement Line Items New Accounting Pronouncement Early Adoption Table [Text Block] Schedule of Short-Term Investments Subject to Fair Value Measurements on a Recurring Basis Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Schedule of Accrued Liabilities Schedule Of Accrued Liabilities Table [Text Block] Summary of Contracts Assets and Liabilities Contract With Customer Asset And Liability Table [Text Block] Schedule of Activities Under Company's Stock Option Plans Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Total Stock-based Compensation Recognized Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Summary of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Net proceeds from issuance of common stock. Description of business. Description of business. Description Of Business [Table] Description Of Business [Table] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] Underwritten public offering. Underwritten Public Offering Underwritten Public Offering [Member] Underwriters Over Allotment Option [Member] Description of Business [Line Items] Description Of Business [Line Items] Issuance of common stock, shares Stock Issued During Period Shares New Issues Common stock price, per share Shares Issued Price Per Share Net proceeds from sale of common stock Net Proceeds From Issuance Of Common Stock Underwriting discounts and commissions and offering expenses Cash And Cash Equivalents [Abstract] Total Summary of significant accounting policies. Summary of significant accounting policies. Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Initial Application Period Cumulative Effect Transition Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition Initial Application Period Cumulative Effect Transition [Domain] Adjustments Difference Between Revenue Guidance In Effect Before And After Topic606 [Member] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Increase in accumulated deficit balance New Accounting Pronouncements Or Change In Accounting Principle [Table] New Accounting Pronouncements Or Change In Accounting Principle [Table] Balances Under ASC 605 Calculated Under Revenue Guidance In Effect Before Topic606 [Member] New Accounting Pronouncements Or Change In Accounting Principle [Line Items] New Accounting Pronouncements Or Change In Accounting Principle [Line Items] Liabilities Liabilities [Abstract] Stockholders' Equity Revenue Loss from operations Loss before provision for income taxes Provision for income taxes Cash flows from operating activities: Net Cash Provided By Used In Operating Activities Continuing Operations [Abstract] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Level I Fair Value Inputs Level1 [Member] Asset Class Fair Value By Asset Class [Axis] Asset Class Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation By Asset Class [Domain] Money market funds Money Market Funds [Member] Money market funds included in restricted cash. Restricted cash (money market funds) Money Market Funds Included In Restricted Cash [Member] U. S. government bonds U S Treasury And Government [Member] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Amortized Cost Available For Sale Debt Securities Amortized Cost Basis Gross Unrealized Holding Gains Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax Gross Unrealized Holding Losses Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax Aggregate Fair Value Available For Sale Securities Debt Securities Contractual maturities of longer than one year Available For Sale Securities Debt Maturities Within One Year Fair Value Accrued research and clinical current. Research and clinical expenses Accrued Research And Clinical Current Payroll and related expenses Employee Related Liabilities Current Legal and professional expenses Accrued Professional Fees Current Other accrued expenses Other Accrued Liabilities Current Total Percentage of net Income or net losses related to development costs. Number of collaboration agreements. Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table] Counterparty Name Counterparty Name [Axis] Counterparty Name Repurchase Agreement Counterparty Name [Domain] AbbVie Ireland Unlimited Company. AbbVie Ireland Unlimited Company Abb Vie Ireland Unlimited Company [Member] Type of Arrangement and Non-arrangement Transactions Type Of Arrangement [Axis] Arrangements and Non-arrangement Transactions Arrangements And Nonarrangement Transactions [Member] Collaborative Arrangement Collaborative Arrangement [Member] Range Range [Axis] Range Range [Member] Minimum Minimum [Member] Maximum Maximum [Member] Geographical Statement Geographical [Axis] Geographical Segment Geographical [Domain] U.S UNITED STATES CD 71 agreement. CD71 Agreement C D71 Agreement [Member] Seattle genetics agreement. Seattle Genetics Agreement Seattle Genetics Agreement [Member] Discovery agreement. Discovery Agreement Discovery Agreement [Member] Contingent Consideration by Type Contingent Consideration By Type [Axis] Contingent Consideration Type Contingent Consideration Type [Domain] Development regulatory and commercial milestone payments. Development, Regulatory and Commercial Milestone Payments Development Regulatory And Commercial Milestone Payments [Member] Sublicense agreement. Sublicense Agreement Sublicense Agreement [Member] Deferred Revenue Arrangement Type Deferred Revenue Arrangement Type [Axis] Deferred Revenue Deferred Revenue Arrangement Type [Domain] Up Front Payment Arrangement Up Front Payment Arrangement [Member] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others By Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type Research And Development Arrangement Contract To Perform For Others Type [Domain] Regents of the university of California. UC Regents Regents Of The University Of California [Member] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items] Number of collaboration agreements Number Of Collaboration Agreements Percentage of net profits or net losses related to development costs Percentage Of Net Income Or Net Losses Related To Development Costs Contingent payments receivable profit split on sales. Contingent payments receivable upon achieving development, regulatory and commercial milestones. Milestone payments received from revenue recognized during period. Payments of sublicense fees. Upfront payment received Proceeds From Collaborators Contingent payments receivable upon achieving development, regulatory and commercial milestones Contingent Payments Receivable Upon Achieving Development Regulatory And Commercial Milestones Profit split on U.S. sales and royalties on ex U.S. sales Contingent Payments Receivable Profit Split On Sales Milestone payment received Milestone Payments Received From Revenue Recognized During Period Sublicense fees paid Payments Of Sublicense Fees Number of targets. Number of targets selected. Number of targets Number Of Targets Number of targets selected Number Of Targets Selected Future contingent milestone payment receivable. Contingent milestone payments receivable Contingent Milestone Payments Receivable Number of accounting units. Estimated research service period. Aggregate collaboration transaction amount. Estimated sublicense fees. Milestone payments receivable. Royalty payment percentage equivalence to sublicense proceeds. Accrued sublicense fees. Revenue adjustment of milestone payment recognized. Total transaction price Aggregate Collaboration Transaction Amount Estimated sublicense fees Estimated Sublicense Fees Number of accounting units Number Of Accounting Units Milestone payment received Milestone Payments Receivable Revenue adjustment of milestone payment recognized Revenue Adjustment Of Milestone Payment Recognized Royalty payment percentage Royalty Payment Percentage Equivalence To Sublicense Proceeds Accrued sublicense fees Accrued Sublicense Fees Revenue recognition upon performance obligation, service period Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1 Revenue recognition upon performance obligation Revenue Remaining Performance Obligation Estimated research service period Estimated Research Service Period Revenue recognized from collaborative arrangement Deferred revenue Contract With Customer Liability Amount due from agreement Contract With Customer Asset Net Common stock shares issuable under agreement. Period used to calculate weighted average price per share. Lock-up period for share transaction under collaboration and license agreement. Estimated premium on issuance of shares. Collaboration and license agreement. Collaboration and License Agreement Collaboration And License Agreement [Member] Amgen Inc. Amgen Inc Amgen Inc [Member] EGFR Products. EGFR Products E G F R Products [Member] Amgen other products. Amgen Other Products Amgen Other Products [Member] Common stock, shares issuable under agreement Common Stock Shares Issuable Under Agreement Common stock, shares issuable under agreement, price per share Share Price Common stock, value of shares issued in connection with agreement Period used to calculate weighted average price per share Period Used To Calculate Weighted Average Price Per Share Lock-up period for share disposal Lock Up Period For Share Transaction Under Collaboration And License Agreement Estimated premium on the stock sold Estimated Premium On Issuance Of Shares Profit share upon exercise of co-development option. Percentage share of profit and losses Profit Share Upon Exercise Of Co Development Option Number of additional collaboration target. Number of additional collaboration target Number Of Additional Collaboration Target Contingent payments payable upon achieving development regulatory and commercial milestones. Contingent payments payable Contingent Payments Payable Upon Achieving Development Regulatory And Commercial Milestones Premium on issuance of shares allocated to common stock. Estimated fair value of products. Portion of transaction price allocated to premium on sale of common stock Premium On Issuance Of Shares Allocated To Common Stock Estimated fair value of products Estimated Fair Value Of Products Number of oncology target. Number of collaboration target. Collaboration target research term. Period of nomination of additional target. Extension of research term for each collaboration target. Increments of extended collaboration target research times. Bristol-Myers Squibb Company. Bristol Myers Squibb Company Bristol Myers Squibb Company [Member] Achieving additional targets. Each Of Two Additional Targets Achieving Additional Targets [Member] Achievement of development milestones for each research target program. Achievement Of Development Milestones For Each Research Target Program Achievement Of Development Milestones For Each Research Target Program [Member] Achievement of development milestones if four research targets selected by counterparty. Achievement Of Development Milestones If Four Research Targets Selected By Counterparty Achievement Of Development Milestones If Four Research Targets Selected By Counterparty [Member] Upon first commercial sale. Achieving First Commercial Sale In Various Territories Achieving First Commercial Sale In Various Territories [Member] Achieving first commercial sale if four research targets selected by counterparty. Achieving First Commercial Sale If Four Research Targets Selected By Counterparty Achieving First Commercial Sale If Four Research Targets Selected By Counterparty [Member] Achieving sales milestones for each research target program. Achieving Sales Milestones For Each Research Target Program Achieving Sales Milestones For Each Research Target Program [Member] Achieving sales milestones if four research targets selected by counterparty. Achieving Sales Milestones If Four Research Targets Selected By Counterparty Achieving Sales Milestones If Four Research Targets Selected By Counterparty [Member] Clinical candidate. Clinical Candidate Clinical Candidate [Member] Achievement of development milestones if eight research targets selected by counterparty. Achievement of Development Milestones if Eight Research Targets Selected by Counterparty Achievement Of Development Milestones If Eight Research Targets Selected By Counterparty [Member] Achieving eight targets selected for first product modality. Achieving Eight Targets Selected for the First Product Modality Achieving Eight Targets Selected For First Product Modality [Member] Achieving sales milestones if eight research targets selected for first product modality. Achieving Sales Milestones if Eight Research Targets Selected for First Product Modality Achieving Sales Milestones If Eight Research Targets Selected For First Product Modality [Member] Achieving development milestone payments. Achieving Development Milestone Payments Achieving Development Milestone Payments [Member] Achieving development milestone payment if eight research targets are selected for second product modality. Achieving Development Milestone Payment if Eight Targets are Selected for Second Product Modality Achieving Development Milestone Payment If Eight Research Targets Are Selected For Second Product Modality [Member] Milestone payments for the first commercial sale in various territories for up to three indications. Achieving Milestone Payments for First Commercial Sale in Various Territories for Up to Three Indication Achieving Milestone Payments For First Commercial Sale In Various Territories For Up To Three Indications [Member] Achieving milestone payment if eight research target are selected for second product modality. Achieving Development Milestone Payment if Eight Targets are Selected for Second Product Modality Achieving Milestone Payment If Eight Research Target Are Selected For Second Product Modality [Member] Achieving sales milestone payments. Achieving Sales Milestone Payments Achieving Sales Milestone Payments [Member] Achieving sales milestone payment if eight research target are selected for second product modality. Achieving Sales Milestone Payment if Eight Research Target are selected for Second Product Modality Achieving Sales Milestone Payment If Eight Research Target Are Selected For Second Product Modality [Member] Number of oncology target Number Of Oncology Target Number of collaboration target Number Of Collaboration Target Collaboration target research term Collaboration Target Research Term Research terms Research And Development Arrangement Contract To Perform For Others Description And Terms Period of nomination of additional target from effective date Period Of Nomination Of Additional Target Extension of research term for each collaboration target Extension Of Research Term For Each Collaboration Target Times of increments for extended collaboration target research time Increments Of Extended Collaboration Target Research Times Future contingent milestone payment receivable terminated. Number of research targets selected. Number of sales indicators for each research target program. Aggregate future contingent milestone payment Contingent Milestone Payments Receivable Terminated Number of research targets selected Number Of Research Targets Selected Number of sales indicators Number Of Sales Indicators For Each Research Target Program Number of non-oncology target. Number of non-oncology target Number Of Non Oncology Target Research and development service fees. Estimated research service termination date. Upfront payment received Research And Development Service Fees Estimated research service termination date Estimated Research Service Termination Date Cash payment to execute the agreement. ImmunoGen, Inc. Immuno Gen Inc Immuno Gen Inc [Member] Transaction Type Transaction Type [Axis] Transaction Transaction [Domain] License receivables. Licenses Received License Receivables [Member] Research services, joint research committee participation and technology improvements. Research Services, Joint Research Committee Participation and Technology Improvements Research Services Joint Research Committee Participation And Technology Improvements [Member] Upfront cash payment Cash Payment To Execute Agreement Milestones payments made during period. Milestone payment accrued. Contingent payments receivable upon achieving development and regulatory milestones. Expected receivable from sales mile stone payments. Contingent payments payable upon achieving development and regulatory milestones. Contingent payments payable upon achieving sales milestones. Contingent payments receivable upon achieving development and regulatory milestones Contingent Payments Receivable Upon Achieving Development And Regulatory Milestones Contingent payments receivable upon achieving sales milestones Contingent Payments Receivable Upon Achieving Sales Milestones Contingent payments payable upon achieving development and regulatory milestones Contingent Payments Payable Upon Achieving Development And Regulatory Milestones Contingent payments payable upon achieving sales milestones Contingent Payments Payable Upon Achieving Sales Milestones Milestones payments made during period Milestones Payments Made During Period Milestone payments accrued Milestone Payment Accrued Estimated total fair value consideration recorded as deferred revenue Estimated fair value of assets and services. Estimated fair value of assets and services Estimated Fair Value Of Assets And Services Option expiration date. MD Anderson. MD Anderson M D Anderson [Member] Option expiration date Options Expiration Date Number of nominated research targets. Number of additional research targets. Contract with customer liability additions. Pfizer Inc. Pfizer Inc Pfizer Inc [Member] Number of research targets Number Of Nominated Research Targets Nominated number of additional research targets Number Of Additional Research Targets With Nomination Option Additional target as deferred revenue Contract With Customer Liability Additions Remaining deferred revenue recognized Contract With Customer Liability Revenue Recognized Amortization period of deferred revenue. Adjusted amortization period of deferred revenue Amortization Period Of Deferred Revenue Contract with customer, liability, accounting standards codification 606 adoption adjustment. Revenue From Contract With Customer [Abstract] Balance as of December 31, 2017 ASC 606 Adoption Adjustment Contract With Customer Liability Accounting Standards Codification606 Adoption Adjustment Additions, Adjustment to Transaction Price from Performance Obligation Satisfied Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Measure Of Progress Deductions to Revenue Recognized from an Adjustment to Transaction Price During the Period Contract With Customer Liability Cumulative Catch Up Adjustment To Revenue Change In Estimate Of Transaction Price Deductions to Revenue Recognized from Amounts Included in Contract Liability at the Beginning of the Period Balance as of September 30, 2018 Adjustment to transaction price from performance obligation satisfied. Adjustment to transaction price from performance obligation satisfied Adjustment To Transaction Price From Performance Obligation Satisfied Revenue recognized based on estimated percentage completed to-date Deductions to deferred revenue recognized during the period Contract with customer liability maturity date. Deferred revenue recognition maturity date Contract With Customer Liability Maturity Date Schedule Of Research And Development Arrangement Contract To Perform For Others [Table] Schedule Of Research And Development Arrangement Contract To Perform For Others [Table] University of California, Santa Barbara. UCSB University Of California Santa Barbara [Member] License Agreement [Line Items] Research And Development Arrangement Contract To Perform For Others [Line Items] Milestone and minimum annual royalty provision paid. Milestone and minimum annual royalty provision paid Milestone And Minimum Annual Royalty Provision Paid Royalty obligations future minimum payments due. Period of time to terminate license after notice date. Annual minimum royalty obligations Royalty Obligations Future Minimum Payments Due License termination period License Termination Period Number of Options Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward Balances, beginning of the period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Options exercised Stock Issued During Period Shares Stock Options Exercised Option forfeited/expired Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures In Period Balances, end of the period Options exercisable, end of the period Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Options Outstanding, Weighted-Average Exercise Price Per Share Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Rollforward Balances, beginning of the period Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Options granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Options exercised Share Based Compensation Arrangements By Share Based Payment Award Options Exercises In Period Weighted Average Exercise Price Option forfeited/expired Share Based Compensation Arrangements By Share Based Payment Award Options Forfeitures In Period Weighted Average Exercise Price Balances, end of the period Options exercisable, end of the period Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Research and development Research And Development Expense [Member] General and administrative General And Administrative Expense [Member] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Stock-based compensation expense: Share Based Compensation [Abstract] Stock-based compensation expense Allocated Share Based Compensation Expense Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Derivative Instrument Derivative Instrument Risk [Axis] Derivative Contract Derivative Contract Type [Domain] Options to purchase common stock Stock Option [Member] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Anti-dilutive securities excluded from computation of diluted net loss per share Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Effective tax rate Effective Income Tax Rate Continuing Operations Federal statutory income tax rate Effective Income Tax Rate Reconciliation At Federal Statutory Income Tax Rate Amount of reasonable estimate for income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act for which accounting for tax effect is incomplete. Indicates (true false) whether accounting for income tax effect of Tax Cuts and Jobs Act is complete. Tax Cuts and Jobs Act, accounting complete Tax Cuts And Jobs Act Accounting Complete True False Tax Cuts and Jobs Act, incomplete accounting, change in tax rate, adjustments Tax Cuts And Jobs Act Incomplete Accounting Change In Tax Rate Provisional Income Tax Expense Benefit